Florida plant detectives are on the trail of a slippery foe, an invasive African land snail that is wily, potentially infectious, and can grow as big as a tennis shoe.

In the four years since Giant African Snails were discovered in Miami, they have slowly but surely spread to new territory, alarming residents in the southern suburbs and the neighboring county of Broward.

Their slimy tracks have led agricultural experts on an odyssey of discovery about animal behavior, folk religion and the precise amount of chemicals and cash it takes to kill the world's biggest gastropods.

The snails are voracious consumers of as many as 500 different plants, and are also known to eat the stucco off houses.

If they consume infected rat feces, the snails can carry a parasitic worm that is dangerous to humans and can cause a rare form of meningitis.

They are also huge. The biggest one found in Florida was nearly seven inches (18 centimeters) long.

At first, officials tried to kill the giant snails with organic pesticides, to no avail. Then they switched to a molluscicide containing metaldehyde, which kills them 95 to 100 percent of the time.

But the snails sometimes climb trees to avoid the chemical pellets on the ground, said Florida Department of Agriculture scientist Mary Yong Cong, who keeps a few in her Miami office to observe their behavior.

"They are very curious," she said, holding one in her hand as it extended its tentacle-eyes toward a visiting reporter.

Adding to their reproductive success, the snails are hermaphrodites, and they can lay up to 1,200 eggs per year. Their eggs look like miniature chicken eggs, each about the size of a Tic Tac.

The snails can disappear for months, hibernating below ground, only to resurface in hurricane season when it is warm and wet.

Officials have set up a snail-sighting hotline, and regularly dispatch workers armed with gloves and rakes to help clear them away.

No one is really sure how the snails got to Florida, but some believe they were smuggled in by people who practice Afro-Caribbean folk religions which use the snails in their rituals.

When the snails were first discovered in south Florida, Santeria was blamed.

"As always takes place, everything that is strange gets labeled under my religion, Santeria," said Ernesto Pichardo, a leading expert and practitioner.

"And we were all like, 'Excuse me, no! This is the first time I have ever seen this beast,'" he recalled.

"It does what? It eats stucco?"

Rather, Santeria uses the small, native Florida snails occasionally in ritual offerings to honor creation, but they are never eaten, he said. Either they are killed or let go after the ritual is over.

Pichardo said Giant African Snails are instead used by traditionalists of the Yoruba people, native to Nigeria and some neighbouring parts of West Africa, who believe drinking the snail's mucus can cure certain ailments.

Since it is illegal to possess Giant African Snails in Florida, the practice remains cloaked in secrecy.

Officials are not aware of any cases of illness due to giant snail ingestion in Miami, but they say the risk is real.

Imagine you have to carry a shell on your back and that you're driven to eat the right foods to nourish that shell, and that some consider you a pest while others consider you food. Now take into account that you're so slow that anything that wants to eat you probably can -- you're not a fleet-footed evader of predators.
Welcome to the life of a snail. You'll never find 100% agreement that they're cute, but there's no denying that their grim determination makes them at least a bit noble. (OK, that might be a bridge too far, but you get the idea!) Herein we take a look at some of these slow-moving critters.
Of course, the shell is a snail's biggest show-stopper. They'll vary widely in color by species and are usually made of calcium carbonate, forming a spiral shape.
To make a shell, snails use a bit of their own hardware called a mantle -- a thin, skin-like organ that secretes a liquid made up of shell material. The liquid hardens and forms the shell. Over time, the mantle releases yet more liquid, adding to the size of the shell.

Snails can be nearly invisible to the naked eye or reach more than 1 foot long. They're found in fresh water, salt water, and on land.
They get knocked for their, well, snail-like pace, but it's not like snails can't move at all. Locomotion for most snails is by means of a large flat foot -- more like a body-length muscle -- underneath them that helps them glide across layers of mucus they secrete to smooth their way forward. It will even leave some slime in its wake, if you watch closely for it.
You might be wondering

how

slow they are. Given it's football season, we'll use 100 yards as a metric. If a garden snail were to receive a kickoff in its end zone and return it all the way for a touchdown, you would have to wait about two hours to see it reach the other end and spike the ball. And garden snails are the absolute speedsters of the snail world!

Land snails will typically eat fruit, dead plants, some live plants, and even bark. Freshwater snails will feast on algae, dead marine life remains and plants, while sea snails enjoy algae as their main course.
Snails have rows of small teeth that sit in long, tongue-like organs called radulas. They don't chew their food so much as grind and tear it with these teeth.

Of course, food in the animal kingdom is often a two-way street: You're either eating or being eaten. A snail has plenty of things that would like to eat it, so that's where its shell comes in. If a predator like a snake or a bird is nearby, a snail can crawl in its shell and seal it off. It can stay holed up like that for days to weeks if it wants to.

Remember the mantle, the snail's organ that secretes material for the shell? Land snails breathe using a lung set into it.
Sea snails, meanwhile, breathe through gills. Like fish, they use them to get oxygen from the water. Freshwater snails sometimes have gills, too, while others have lungs. When the latter need to breathe air, they surface and take a gulp.

Land snail eggs are not much bigger than a letter on your computer screen. Over a couple of days, a land snail will lay up to 100 eggs, burying them in shallow holes covered with dirt and their own slime. Most won't survive predation; those that do will hatch in 2-4 weeks.
Sea snails will deposit their eggs by the thousands on the ocean floor, though most won't fare any better than those on land. Freshwater snails may deposit their eggs above the water line, such as those of the apple snail, shown here.

Unfortunately for them, some species of snail, such as abalones and some land snails, are eaten by people. France, for example, raises them for that purpose. (Snail fans who don't see them as food will want to avert their eyes from escargot.)

Most snails are hermaphrodites, with both male and female reproductive organs. A mating ritual that can last several hours results in each snail having eggs to deliver, after they grow for a bit inside the snail. As we've seen, most young'ins won't make it, but a few will, and snails will find a way to keep on going.